Incremental Sheet Forming Process Research Articles

Optimization Of Process Parameters For Incremental Forming Of Aluminium 1060

In the past two decades, extensive research was done on incremental sheet forming (ISF). It has resulted in significant advances in fundamental understanding and the development of new processing and tooling solutions. However, ISF is yet to be fully implemented in mainstream high-value manufacturing industries due to a number of technical challenges, all of which are directly related to ISF process parameters. Now a days, the demand for new materials for sheet plate has become high in the number of applications because of various attributes in the material such as high tensile strength, good flexibility and durability. The present work gives the effect of several process parameters such as tool rotating speed, step size(z-axis), and feed (x-y axis) on forming force of incremental forming. Particular attention is given to the deformation rate and stress developed in the material during incremental forming. The tool path for incremental forming is generated using MATLAB software. Simulations are done using Taguchi’s L9 orthogonal array method. All the simulations are done in Abaqus software. Stress developed in the material during incremental forming is determined in the simulations. The effect of each process parameter on the stress developed is investigated. Finally, Optimization of the Process parameters is done for Incremental forming process. ANOVA technique is used to find the influence of each process parameter on the stress developed in the material

Understanding a new wrinkling behavior of annular grooved panel during flexible free incremental sheet forming

Wrinkling behavior of sheet metal by inappropriate process parameters and the resultant variation of thickness and microstructure during incremental sheet forming (ISF) have significant impact on forming stability and geometric profile. The wrinkling-related mechanism is yet to be well understood, which make it difficult to effectively control wrinkling defects during ISF. In the present work, the wrinkling behavior and related mechanism of a typical annular grooved panel are investigated during a novel flexible free ISF process. Experiments demonstrate that during this ISF process, the sheet material sequentially undergoes 4 deformation modes: contacting state under plane strain condition, contracting state with only elastic deflection, thickening state under uniaxial compression condition, and wrinkling state where the circumferential compressive stress exceeds the critical wrinkling stress. The evolution of these deformation modes is dominantly caused by the increasing of edge contraction and circumferential stress, which are induced by the bending moment from the forming tool and auxiliary sheets. Based on the mechanism, an analytical model is developed to predict the wrinkling behavior, by which the corresponded sheet thickness, bending moment, circumferential compressive stress and critical wrinkling stress during the wrinkling process could be comprehensively calculated. Experimental results validate that the analytical model can accurately predict the wrinkling behavior under different process parameters, material properties and auxiliary sheet materials. Through microstructural characterization, numerical simulation and analytical modeling, the influence of process parameter and material property on wrinkling behavior is systematically investigated, along with the variation of sheet thickness and microstructure under different wrinkling modes. This work enhance a deep understanding of wrinkling behavior during ISF process, thereby providing effective methods for process optimization and quality improvement.

Critical state-of-the-art literature review of surface roughness in incremental sheet forming: A comparative analysis

Incremental sheet forming (ISF) is a controlled and die-less forming process that can produce customized products from the sheets layer by layer using the same setup, i.e., forming tools and machine. This novel and emerging forming technique can potentially be useful as a green aspect of manufacturing by reducing the required power and by saving the resources for producing the components of lightweight materials because material is deformed locally during ISF. The surface quality of the formed parts from sheet material affects the aesthetics aspects, stress concentration, fatigue life and their applicability. This review article aims to provide a state-of-the-art review for various aspects and parameters of ISF process that affect the surface roughness significantly by conducting literature survey quantitatively. Furthermore, the techniques of ISF and roles of various parameters responsible for affecting the surface quality of parts have also been explored for providing the critics for existing literature and setting the further guidelines for the researchers. Various instruments used for measuring the surface roughness of parts formed by ISF has also been discussed. Comparative analysis of exiting literature available in the context of various process parameters, ISF hardware, and surface roughness makes this study comprehensive and exhaustive for the researchers to find the gaps and challenges in this field. The relationship of wall angle with other process parameters can be explored in the future to obtain the desired surface quality of a particular material. Significant parameters responsible for the surface quality have also been discussed critically. Further, the new tool paths can be developed for high surface quality and low forming time. A study on the selection of feed rate for various applications and relation with other parameter is also recommended for the future work. The lubricants with additives can further be tested for high surface quality of ISF. Further, significant study on surface roughness is not conducted on hybrid sheet forming and other advanced variants of ISF (like hot forming, friction stir assisted incremental forming, waterjet forming). It is required to develop the comparisons between the different techniques of ISF. Results also showed that majority of researchers used SPIF technique followed by DSIF and hybrid ISF.

Optimization of Ultrasonic-Assisted Incremental Sheet Forming.

Implementing the ultrasonic vibration-assisted incremental sheet-forming (UISF) process has been proven to significantly reduce the forming force, improve the surface quality, and enhance the accuracy of the sheet-forming process. However, such effectiveness has primarily focused on easily deformable materials (such as AA1050 and AA1060 aluminum alloys) and small step-down sizes (from 0.3 mm to 0.5 mm). To further enhance the process, it is crucial to study larger step-down sizes and harder materials. In this study, a series of UISF experiments were conducted, with step-down sizes ranging from 0.5 mm to 1.5 mm and feed rates ranging from 200 mm/min to 1200 mm/min. The influence of ultrasonic vibration on the effectiveness of force reduction and the optimal operation parameters was experimentally tested. Forming aluminum alloy AA5052, a difficult-to-deform material with two thicknesses of 0.5 mm and 1.0 mm, indicates that the axial force Fz and the tool movement resistance force Fy tend to decrease significantly with ultrasonic vibration assistance. Optimal equations for force reduction Fz and Fy have been developed for plate thickness based on the step-down size and feed rate. The optimal results show that for 1.0 mm thickness, reductions in Fz and Fy can reach 58.73% and 69.17%, respectively, and that of 64.17% and 71.98%, respectively, for 0.5 mm thickness.

Improving the Room Temperature Formability of Magnesium AZ31B Alloy Sheets during the Incremental Sheet Forming Process

Improving the Room Temperature Formability of Magnesium AZ31B Alloy Sheets during the Incremental Sheet Forming Process

Friction and heat partition coefficients in incremental sheet forming process

To understand the thermo-mechanical behaviour in incremental sheet forming (ISF), it is important to precisely determine the interfacial and thermal-relevant parameters including coefficient of friction (COF) and heat partition coefficient (HPC), and to characterise the effect of thermo-mechanically induced heat generation under ISF processing conditions. In the present study, a new tool path-defined straight groove test combined with mechanical and thermal detection is proposed to determine the COF and HPC of Aluminium alloy (AA1050) and commercially pure titanium Grade 1 (CP Ti Grade 1) sheets. The experimental and numerical results show that the determined COF and HPC values are sufficiently accurate. The interaction between friction force and thermal response is observed by this testing method. A novel theoretical thermal model is developed to correlate the relationship between friction-induced heat generation and the thermal effect. The results indicate that the new theoretical model can capture the temperature distribution and variation under different processing conditions, and the results show a good agreement with the finite element (FE) simulation. The presented testing method and theoretical model provide an insight into the determination of the thermal-relevant parameters (COF and HPC), and the quantification of the effect of friction-induced heat generation on the thermal response of the materials.

Advanced FEM Insights into Pressure-Assisted Warm Single-Point Incremental Forming of Ti-6Al-4V Titanium Alloy Sheet Metal

This study employs the finite element (FE) method to analyze the Incremental Sheet Forming (ISF) process of Ti-6Al-4V titanium alloy. The numerical modeling of pressure-assisted warm forming of Ti-6Al-4V sheets with combined oil-heating and friction stir rotation-assisted heating of the workpiece is presented in this article. The thermo-mechanical FE-based numerical model took into account the characteristics of the mechanical properties of the sheet along with the temperature. The experimental conditions were replicated in FEM simulations conducted in Abaqus/Explicit, which incorporated boundary conditions and evaluated various mesh sizes for enhanced accuracy and efficiency. The simulation outcomes were compared with actual experimental results to validate the FE-based model’s predictive capacity. The maximum temperature of the tool measured using infrared camera was approximately 326 °C. Different mesh sizes were considered. The results of FEM modeling were experimentally validated based on axial forming force and thickness distribution measured using the ARGUS optical measuring system for non-contact acquisition of deformations. The greatest agreement between FEM results and the experimental result of the axial component of forming force was obtained for finite elements with a size of 1 mm. The maximum values of the axial component of forming force determined experimentally and numerically differ by approximately 8%. The variations of the forming force components and thickness distribution predicted by FEM are in good agreement with experimental measurements. The numerical model overestimated the wall thickness with an error of approximately 5%. By focusing on the heating techniques applied to Ti-6Al-4V titanium alloy sheet, this comparative analysis underlines the adaptability and precision of numerical analysis applied in modeling advanced manufacturing processes.

A new analytical model for force prediction in incremental sheet forming

A new analytical model for forming force prediction in the whole process of incremental sheet forming (ISF) is presented in this work. The modelling of contact region, thickness distribution and strain components are carried out as the basis for the prediction of vertical and horizontal forces. The effect of local contact behaviour and material deformation, as well as the behaviours of global bending, changes of deformation mode and contact condition are taken into account in the modelling of ISF force history. The force prediction model at both plane strain and biaxial tension condition areas is developed based on the differences in contact region and thickness distribution between these two different deformation states. Validated by ISF tests for a truncated cone and pyramid part with varying drawing angles, the prediction of force history captures well the fluctuation of different force components due to the change of deformation conditions and provides an insight into the material deformation mechanisms and the direct correlation to forming force characteristics of the whole ISF process. In a practical case, the model is successfully applied to the force prediction in ISF-based cranial plate manufacture. The model is also validated by a series of ISF tests with accurate force predictions of both the peak and stabilised forces.

A framework for predicting grain morphology during incremental sheet metal forming using generative adversarial networks

Properties and service performance of parts and components depend upon microstructural characteristics including grain morphology, size and size distribution, and crystallographic orientation. Microstructure itself is dictated by manufacturing process parameters. Microstructural analysis is often necessary for evaluating product quality. Past research has attempted to map product/process characteristics using analytical, numerical, and experimental approaches. To address the limitations of conventional modeling approaches, researchers have begun to explore the application of artificial intelligence (AI) techniques in correlating and predicting the effect of process parameters on material microstructure and mechanical properties. For instance, AI-based approaches have been used to model the influence of process parameters on forming force, formability, geometric accuracy, tool path, and surface quality in incremental sheet forming (ISF), a flexible forming process suitable for low-volume and custom product manufacturing. The research reported herein introduces a framework to map ISF process parameters to microstructural images using Generative Adversarial Networks (GAN). This approach can reduce the experimental and analytical effort and costs typically necessary to evaluate the effects of ISF process settings on material microstructure and mechanical properties.

Reviews on the Effect of Single Point Incremental Forming (SPIF) Process Parameters on Surface Roughness of Aluminum Alloy AA1050-H14 Sheet Metal

Incremental Sheet Forming (ISF) is emerging as one of the popular dieless forming processes for the small-sized batch production of sheet metal components. However, the parts formed by the ISF process suffer from poor surface finish, geometric inaccuracy, and non-uniform thinning, which leads to poor part characteristics. This paper deals with the influence of single point continuous local forming process parameters on the surface roughness of the product. Design of trials used for research planning and analysis and interpretation of results. The results indicate that the tool diameter (D), vertical step-down size (Δz), and sheet thickness (t) have significant effects on the produced profile accuracy, while the feed rate (f) is not significant. As a general rule, thin sheets with greater tool diameters yielded the best surface quality. The results also show that controlling all surface quality features is complex because of the contradicting effects of, and interactions between, a number of the process parameters.

Failure mechanism during incremental sheet forming of a commercial purity aluminum alloy

Incremental sheet forming (ISF) is known for many advantages over conventional forming, such as part flexibility, low tooling cost and higher formability. Previously various studies have explored the failure mechanism experimentally and numerically. However, limited studies have been performed on the micro-mechanics of failure during ISF process. This study involves failure mechanism during incremental sheet forming of a commercial purity aluminum alloy (AA1050). During experiments, failure (fracture) was observed in truncated cone specimens by increasing the wall angle from 71° to 72°. The mechanism behind failure was explored with detailed microstructural characterization and finite element (FE) simulations. Various samples were taken from the successfully formed and failed cones for microstructural analysis. The electron backscatter diffraction (EBSD) based microtexture measurements associate this failure with more grain fragmentation and necking or localized deformation in the failed cone. Further, the X-ray diffraction (XRD) based residual stress measurements indicate high positive (tensile) hydrostatic stresses (∼157 MPa) on the outer surface of the failed (fractured) cones. Finite element analysis (FEA) with Gurson-Tvergaard-Needleman (GTN) damage model was used for fracture prediction. The FEA results also support the residual hydrostatic stress evolution in the cones, albeit at a slightly different wall angle. Based on microstructural and finite element analysis it is concluded that deformation becomes inhomogeneous when the failure occurs during ISF process.

Experimental Investigation and Optimization of AZ31 Mg alloy during Warm Incremental Sheet Forming to Study Fracture and Forming Behaviour

The main purpose of this research work is to study the forming limit and fracture behaviour of the AZ31 magnesium alloy, as well as to improve the formability and surface roughness of parts formed using the warm incremental sheet forming (ISF) process. For the ISF process, AZ31 Mg alloy sheets were used. Initially, Taguchi orthogonal L27 arrays were used to design experiments, and a framed multi-objective optimization problem was solved using the grey-fuzzy method. The strain-based forming fracture limit diagrams (FFLD) were plotted after a variable wall angle test. The grey-fuzzy reasoning grade (GFRG) is calculated in this study by combining grey relational analysis (GRA) and fuzzy rationale. For the AZ31 Mg alloy, the maximum GFRG value was obtained for the following forming combinations: step depth 0.3 mm, feed rate 500 mm/min, spindle speed 700 rpm, and tool diameter 10 mm. Then, ANOVA was used to determine the importance of parameters on the responses, and it was discovered that the step depth has the greatest influence (68.78%) on GFRG value, followed by the feed rate (16.56%). The fracture behaviour of the Mg alloy was studied using fractographs. Later, FE simulation was used to validate the strain value obtained from experimentation and to investigate the effect of process parameters on responses.

A review on the effect of residual stresses in incremental sheet metal forming used in automotive and medical sectors

Incremental sheet forming (ISF) is a process that can produce sheet metal components with a series of stepwise small incremental deformation. This literature paper presents a thorough review of analyzing the influence of residual stresses in correlation with different process variables like tool diameter, tool path, the thickness of the sheet, depth of cut and wall angle, etc., during the procedure of single point incremental forming used in the automotive and medical industry. Moreover, this paper clearly explains the process parameters, which further help improve the ISF process compared to other conventional metal forming processes. This review initiates with the introduction of ISF for different types of materials and follows the residual stress measurement in various sectors. This paper also provides specific insights into the impact of residual stresses on forming forces, geometric shape accuracy, formability, and other factors in the process. The gap from this intensive review will provide the groundwork for the investigators for future research to recognize the implication of residual stresses in the automotive and medical fields. Based on the investigation, residual stresses should be considered in the design step of the manufacturing process with diverse scales. Finally, the future scope and probable research directions were discussed.

Feature Segmentation of Multifeatured Freeform Geometries for Incremental Sheet Forming

Incremental sheet forming (ISF) of sheets is a flexible forming process that forms a geometry from a clamped sheet using local deformation of the sheet by moving a forming tool along a predefined path. Many factors are responsible for the accessibility and accuracy of forming in the ISF; some of them are forming force, sheet thickness, clamping force, working temperature, and toolpath. One of the important factors which affect the ISF process is the toolpath. However, conventional toolpath generation strategies are designed for the machining process and are not suitable for forming multifeature parts in the case of ISF. A feature segmentation method, which would segregate geometry into multiple features and generate the optimum toolpath with the correct forming sequence, is required to successfully form multifeatured parts through ISF. This paper presents a simple, but an innovative method to segment a component into multiple geometrical features. The proposed method uses the internal characteristics of the STL part file and the number of sliced contours on the parts for feature segmentation.

Comprehensive modeling of forming forces in three directions for incremental sheet forming process based on the contact area

Incremental sheet forming (ISF) is a promising sheet forming process for small batch production of complex 3D workpieces without time consuming set-up operation. However, the understanding of comprehensive effect of the contact area and stress on forming force is still insufficient, which is critical to the feedback control, process optimization and professional machine design, etc. Therefore, the present work aims to provide efficient mechanism-based prediction models for both the contact area, stress and the forming force. First, a universal predicted shape of the contact area between the forming tool and sheet in the ISF process was deduced and modeled based on typical experimental phenomena. In particular, the influence of parameters on the shape of contact area was clarified by defining contact angles β, α and α1. Then, stress components of the material within the contact area were derived after the theoretical analysis by adopting the cylindrical coordinate. In addition, an efficient forming force prediction model for ISF especially in three directions was established and verified, which combined the contact area model and calculated stress components. Finally, it is proved that sheet thickness has the most significant positive effect on forming force in three directions, since the rise of thickness not only increases the size for contact area but also leads to a large growth of equivalent thickness coefficient. Meanwhile, tool diameter has limited effect on forming fore, although it has the largest effect on the size of contact area. This study provides the fundamental understanding of the dynamic interrelation between contact area, stress-strain states and forming forces, which promotes the industrial transformation of ISF.

Process capabilities and future scope of Incremental Sheet Forming (ISF)

The Incremental Sheet Forming process (ISF) is a versatile forming process that is widely used in various advanced manufacturing areas such as for making the skull prosthesis, automobile, electronics and aerospace components etc. In the present paper methods, chronology of ISF and its classifications have been discussed, considering the effect of various factors such as stress triaxiality, bending stress and fracture strain. In addition, the effect of process parameters and its interaction on forming force, formability, surface roughness, spring back, failure and fracture etc. are also studied. It is observed that the study of two degree of freedom manipulator of robot with ISF and its effect on the formability surface roughness are highly recommended. Also, a future scope of ISF is also included in this investigation.

Incremental sheet forming parameters and applications: a review

The present work introduces a literature review on the Incremental Sheet Forming process application and main parameters. This process is used to manufacture small batches of parts and formed sheets prototypes, as a semi-spherical-tipped tool yields form to a sheet using a pre-defined trajectory and various step-downs (Δz). In this work we describe the Incremental Sheet Forming process variations, application examples, the types of machines used and the diagram characteristics that describe the formed material’s strain limits. The article also presents a detailed study on the influence of the main strength parameters required to execute the process, material formability, surface finishing and final product accuracy.

Adaptive increment based uniform sheet stretching in Incremental Sheet Forming (ISF) for curvilinear profiles

Incremental Sheet Forming (ISF) is a rapid prototyping based die-less forming process. In this process, curved end based forming tool deforms the sheet by a user-defined Numerical Control (NC) toolpath. This paper focuses on the formability response of the sheet stretching during the ISF process. The stretching in the axial direction primarily depends on the wall angle of the profile and the incremental depth. During the die-less deformation of the constant wall angle based geometries (truncated cone or pyramid); with each increment uniform stretching of the sheet occurs. However, in case of the variable wall angle-based geometries (curvilinear wall profiles), higher sheet stretching occurs at steep wall angles. Adaptive increment based strategy has been developed for the die-less forming of the curvilinear geometries so that uniform sheet stretching in the axial direction can be sustained. The response of the developed strategy towards sheet formability, equivalent stress and strain distribution has been investigated in this study. For implementation, the toolpath for the Finite Element Analysis (FEA) simulations (ABAQUS®) and experimentation has been defined using an in-house developed Computer-Aided Manufacturing (CAM) module. Experimental and simulation results exhibit the improvement in the sheet thickness and stress distribution.

Numerical Study to Promote the Residual Stresses Development during ISF Process with Improvement in Two Point Incremental Die Forming

Metastable austenitic stainless steel (MASS) has been the material of choice for the fabrication of disc springs employing incremental sheet forming (ISF) processes due to its high creep, fatigue, and chemical resistance, as well as its good surface quality. Previous research has shown that the presence of martensite enhances the formation of beneficial compressive residual stresses. However, if the ISF is accelerated to improve efficiency, the rise in temperature during ISF operation suppresses the deformation that causes martensite transition (DIMT). In essence, the cooling channel shapes are developed with numerical assistance such that its impact on residual stress induction is low. Variation in ISF process parameters, such as tool diameter, tool step-down, and contact force, as well as variation in cooling channel size, are used to construct the computational analysis. To analyze the finally produced residual stresses in the disc spring, the non-linear isotropic/kinematic hardening combined with the TRIP formulation is simulated. According to the comparison, the channel size must be between 0.8 and 1.2 mm in radius to minimize residual stress fluctuation. Additionally, when moving across the die with cooling channels, the force-controlled ISF produces more consistent results. Based on the numerical findings, it is conceivable to greatly enhance the ISF process speed and dissipate process heat by cooling the sheet on sides, allowing residual stresses and martensite content to be adjusted in a stable manner. As a result, the ISF process may be greatly expedited, making it more appealing for industrial applications.

An Investigation of the Impact of Forming Process Parameters in Single Point Incremental Forming Using Experimental and Numerical Verification

Incremental sheet forming (ISF) is an innovative cold forming operation and has enticed great interests owing to its flexibility and capability to manufacture various complex 3D shapes with low costs and minimum requirements. Single point incremental forming (SPIF) is the most popular type of ISF process and has high quality and less occurrence of defects for the formed products if the operating parameters are achieved and evaluated with high precision. In this study, the impact of tool diameter and forming angle on the forming force, thickness distribution, thinning ratio, effective plastic strain, forming depth and fracture behaviour was explored. AA1050 aluminium alloy and DC04 carbon steel were employed to produce a truncated cone in accordance with the SPIF process. A 3D finite element model was required to achieve a well-established investigation. The SPIF of a truncated cone numerical model was adopted to build a model with the same conditions as of the experimental work with aid of ANSYS software version 18 through using the workbench LS-DYNA model. The sheet metal modelling was carried out in accordance the Cowper Symonds power law hardening by taking the behaviour of the material as elastic–plastic, and the anisotropic properties were assumed to simulate the plasticity behaviour for two sheet metals. Results indicate that the DC04 carbon steel has a higher forming force, minimum thickness and lower thinning ratio compared with AA1050 aluminium alloy under the same operating conditions.